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Hot DQ white dwarfs: a pulsational test of the mixing scenario for their formation

Published online by Cambridge University Press:  21 October 2010

A. Romero
Affiliation:
Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Argentina Instituto de Astrofísica La Plata, IALP, CONICET-UNLP
A. H. Córsico
Affiliation:
Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Argentina Instituto de Astrofísica La Plata, IALP, CONICET-UNLP
L. G. Althaus
Affiliation:
Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Argentina Instituto de Astrofísica La Plata, IALP, CONICET-UNLP
E. García-Berro
Affiliation:
Departament de Fisica Aplicada, Escola Politécnica Superior de Castelldefels, Universitat Politécnica de Catalunya Institut d'Estudis Espacials de Catalunya email: [email protected]
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Hot DQ white dwarfs constitute a new class of white dwarf stars, uncovered recently within the framework of SDSS project. There exist nine of them, out of a total of several thousands white dwarfs spectroscopically identified. Recently, three hot DQ white dwarfs have been reported to exhibit photometric variability with periods compatible with pulsation g-modes. In this contribution, we presented the results of a non-adiabatic pulsation analysis of the recently discovered carbon-rich hot DQ white dwarf stars. Our study relies on the full evolutionary models of hot DQ white dwarfs recently developed by Althaus et al. (2009), that consistently cover the whole evolution from the born-again stage to the white dwarf cooling track. Specifically, we performed a stability analysis on white dwarf models from stages before the blue edge of the DBV instability strip (Teff ≈ 30000 K) until the domain of the hot DQ white dwarfs (18000-24000 K), including the transition DB→hot DQ white dwarf. We explore evolutionary models with M*= 0.585M and M* = 0.87M, and two values of thickness of the He-rich envelope (MHe = 2 × 10−7M* and MHe = 10−8M*).

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2010

References

Althaus, L. G., Garcia-Berro, E., Córsico, , et al., 2009, ApJL, 693, L23CrossRefGoogle Scholar